Generally, in printing plate materials comprising a layer composed of a photosensitive resin composition, a photosensitive resin layer contains a soluble polymer, a photo-polymerizable unsaturated group-containing monomer and a photopolymerization initiator as indispensable components, and additives such as a stabilizer and a plasticizer are also incorporated therein as required. Such printing plate materials are used by forming a relief image thereon by irradiating the photosensitive resin layer with ultraviolet light through a negative or positive original image film or an image mask layer that is arranged on the photosensitive resin layer and does not transmit ultraviolet light and thereby forming a solvent-soluble part and a solvent-insoluble part in the photosensitive resin layer.
Most of the photosensitive resin relief priming materials used today are capable of forming a relief when a relief image formed by exposure is developed with water and, as the soluble polymer of the photosensitive resin layer, a water-soluble or water-swellable polymer is used.
Partially saponified polyvinyl acetates and derivatives thereof have been used in many occasions because of their solubility to water and excellent water developability; however, since they have a high crystallization degree are thus weak against impact force repeatedly applied during printing, there is such a problem that relief cracks are generated during printing.
As a method of solving the above-described problem, for example, in Patent Documents 1 and 2, it is proposed to incorporate a polyvinyl acetate derivative and a basic nitrogen-containing polyamide.